Plant Development and Stem Yield of Non‐domestic Fibre Hemp (Cannabis sativa L.) Cultivars in Long‐day Growth Conditions in Finland

Abstract

AbstractPlant development and stem yield of mono‐ and dioecious fibre hemp cultivars (Cannabis sativa L.), introduced to Finland from regions of lower latitude, were studied in field experiments under long‐day growth conditions in 1995–96. Plant density, plant mortality rate, stem elongation and stem yield were determined. Plant densities at seedling stage were less than the targeted viable seeds sown m−2. Seedling densities differed significantly among cultivars, but had no significant effect on plant mortality rate in 1996. Plant mortality during the 1996 growing season averaged 34 plants m−2. Stem elongation was measured at one‐week intervals throughout the growing time. The elongation among cultivars was different and depended on the date of measurement. Rapid elongation began five to six weeks after sowing and elongation was most pronounced in July. Dioecious cultivars were significantly taller than monoecious ones in 1995 but not in 1996 when hemp stands were dense, nitrogen was deficient and an infection of Botrytis vinerea was present. Dioecious cultivars produced higher stem yields than monoecious ones. However, in 1996 the difference in yield was not statistically significant among most of the cultivars, Cultivar Uso 11 was early maturing and produced highest stem yield among monoecious cultivars; it also competed well with the higher yielding dioecious cultivars.